Download Global Change 14 - Notes on Fisheries

Notes on Fisheries
When we can drain the Ocean into mill-ponds, and bottle up the Force of Gravity, to be sold
by retail, in gas jars; then may we hope to comprehend the infinitudes of man's soul under
formulas of Profit and Loss; and rule over this too, as over a patent engine, by checks, and
valves, and balances
- Thomas Carlyle (1795-1881), Scottish essayist, historian. Signs of the Times (1829; first
published in Edinburgh Review no. 98)
Suggested Readings:
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World Resources Institute. 1994. World Resources 1994-95: A guide to the global
environment. Oxford.
Norman Myers, ed. 1993. Gaia: An Atlas of Planet Management, Anchor Books.
U.S. Department of Commerce, 1995. Fisheries of the United States, 1994, NOAA
Current Fisheries Statistics No. 9400.
Gurney, R.J, J.L. Foster, and C. L. Parkinson. 1993. Atlas of Satellite Observations
related to Global Change, Cambridge Press.
In this lecture period, we wish to learn:
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What is the importance of fish in the diet of humans?
What are the important marine resources, and are they harvested sustainably?
What is the sustainable yield of the oceans?
What possible solutions might allow humans to more sensibly obtain food from the
seas?
1. Fish Stocks and Fish Harvests
We can group economically important marine organisms in to five major families:
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Demersal fish. These are bottomliving fish such as cod and haddock.
These species tend to concentrate on
broad continental shelves, especially
of the North Atlantic.
Pelagic fish. Pelagic fishes are species
that inhabit the water column, such as
herring, mackerel, anchovy, and tuna.
The most spectacular fish catches are
made of surface-shoaling pelagic
species. Demersal fishes and Pelagic
fishes combines make up the majority
of the fish catch--about 72 million tons
per year.
Crustaceans. This group consists of
bottom-dwelling species (crabs and
lobsters) as well as swimming
invertebrates (krill,
shrimp)Crustacean fisheries are
important to many countries and
regions, such as the Chesapeake Bay
of the U.S. About 4 million tons of
this group are harvested each year.
Molluscs and Cephalopods. These
include various species of squid,
cuttlefish, and octopus. More
cephalopod stocks are harvested by the
Japanese than by any other nation.
They also serve as an important source
of protein for many Mediterranean and
developing countries. About 2.5
million tons of cephalopods are
harvested each year.
Marine mammals. This group
has been heavily exploited for oil
and meat, although they make a
relatively small portion of the
global fish catch. Following the
commercial extinction of the large
baleen whales such as the blue,
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humpback, and fin, smaller
species such as the minke and
sei are being taken. Dolphins and
porpoises are hunted locally,
particularly in some tropical
archipelagos.
Figure 1: Families of economically important fish
2. The Importance of Fish
Why are we concerned about the status of our global fisheries? In addition to more lofty
environmental reasons, such as the preservation of biodiversity, humans have stock in the
status of our world's fisheries. Here are some statistics to give you an idea of the scope of
human dependence on marine life:
Over 90% of the world's living biomass is contained in the oceans, which cover 71% of
the Earth's surface. At present, we harvest about 0.2% of marine production. (You might
think that there is room for growth).
Marine sources provide about 20% of the animal protein eaten by humans. Another
5% is provided indirectly via livestock fed with fish.
60% of fish consumption is by the developing world.
In Asia, about 1 billion people rely on fish as their primary source of protein.
Estimates suggest that seafood production from wild fish stocks will be insufficient to
meet growing U.S. and Global demand for seafood products in the next century.
The fishing enterprise employs some 200 million people worldwide.
3.Principles and Terms
First, we need to become familiar with some terms used when discussing fish populations
and the fishing industry.
Stock. A stock is the portion of a species or population that is harvestable.
Stock Assessment is the estimation of abundance of a resource, rate at which it is
being removed, and reference rates for sustainable yields.
Fishing Mortality Rate is a function of the fishing effort (amount, types of gear,
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etc.)
Harvest RateThe harvest rate is the fraction or amount of stock harvested per year.
Production Rate. The production rate is the sum of growth in weight of individual fish,
plus the addition of biomass from new recruits, minus loss in biomass to natural mortality.
Production Function shows the relationship between production rate and fishing
effort. As effort increases, the biomass drops and the production function typically goes
through a fairly stable maximum.
To aid in fish management, we can assess stocks by using a combination of three methods:
 biological sampling
 annual catch statistics
 catch per unit effort statistics
Stock assessment and management is becoming increasingly important, as is illustrated by
these statistics on the global harvest history:
 Total catch has climbed fairly steadily since the 1950's.
 Now, about 100 million metric tons/year are taken from the sea. This figure seems to be
stabilizing.
 However, the harvest per capita has grown little (see Figure 2). This implies that if the
current limit can not be increased, seafood availability per person will shrink as
population expands. This will lead to rising prices.
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Figure 2: Global absolute and per capita fish catch, 1950-2000
4. Evidence of Over-Exploitation
We can assemble a large amount of evidence that points to the fact that our marine
resources have been over-exploited. First, there is a long list of over-utilized resources.
These are some species which have been overfished:
 New England groundfish and flounder
 Southeast Spiny Lobster
 Atlantic Bluefin Tuna and Swordfish
 Main Hawaiian Island Bottomfish and Pelagic Armorhead
 Large Coastal Sharks
 Gulf of Mexico King Mackerel and Pink Shrimp
 Atlantic/Gulf of Mexico/Caribbean Reef Fish Complex
 Pacific Ocean Perch
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 North Pacific Albacore
 Oysters, Hard Clams, and Abalones in many location
Secondly, the dates at which over-fishing began for various North Atlantic fisheries are
alarming. From the table below, we can see that as we overfished one species, we simply
moved to another and overfished that as well.
Table 2: Peak catch year of some fish species
Species
Peak
Year
Peak
Catch
1992
Catch
Decline
(in millions of
tons)
Percent
Change
Pacific herring
1964
0.7
0.20
0.5
-71%
Atlantic herring
1966
4.1
1.50
2.6
-63%
Atlantic cod
1968
3.9
1.20
2.7
-69%
South African
Pilchard
1968
1.7
0.10
1.6
-94%
Haddock
1969
1.0
0.20
0.8
-80%
Peruvian anchovy
1970
13.1
5.50
7.6
-58%
Polar cod
1972
0.35
0.02
0.33
-94%
Cape hake
1972
1.1
0.20
0.9
-82%
Silver hake
1973
0.43
0.05
0.38
-88%
Greater yellow
croaker
1974
0.20
0.04
0.16
-80%
Atlantic redfish
1976
0.7
0.30
0.4
-57%
Cape horse mackerel 1977
0.7
0.40
0.3
-46%
Chub mackerel
1978
3.4
0.90
2.5
-74%
Blue whiting
1980
1.1
0.50
1.8
-26%
South American
Pilchard
1985
6.5
3.10
3.4
-52%
Alaska pollock
1986
6.8
0.50
1.8
-26%
North Pacific hake
1987
0.30
0.06
0.24
-80%
Japanese pilchard
1988
5.4
2,5
2.9
-54%
TOTALS
---
51.48
21.77
29.71
-58%
Source: FAO
Finally, specific examples of fishery declines highlight the over-consumption problem.
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5. New Methods, New Targets, and Over-Capacity
Numerous statistics point to over-capacity:
Despite warnings of a slowdown in the marine catch in the 1970's and 80's, the fishing
industry increased fishing efforts. Over the past 40 years, the technology used in fishing has
improved. Now, boats are more powerful, fish are located electronically through sonar,
larger nets are used, and there are just more fishing operations.
Today, the industry is twice as large as necessary. It could go back to the smaller, fewer
boats of 1970 and still produce the same yield. This overcapacity is global: Norway is 60%
over, while the European Union is 40% over. In the U.S., there are ten times the number of
boats needed for the surf clam industry.
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How did this overcapacity develop?
Competition led to an all-comers
welcome approach. More
competition for declining resources
leads to overcapitalization in ever
larger boats and nets.
Drift nets (see Figure 3) are a
spectacular example of the new
more efficient fishing methods.
These monster nets (50 feet by up
to 65 km) kill all that they
encounter. They are banned by
every fishing country within its own
territorial waters. The combination
of Japanese, Korean, and
Figure 3: Drift net in use
Taiwanese drift nets cast every
night in international waters reaches about 48,000 km--enough to encircle the globe.
Another piece of evidence suggesting that we are overharvesting our seas is that we have
been relegated to fishing for previously unfished stocks. We are now eating species
heretofore thought of as "bait".
The Peruvian Anchovy Fishery
To illustrate how overcapacity works, we will study the example of the Peruvian anchovy,
which in boom years was the largest new fishery in the world.
Before 1950, fish in Peru were harvested mainly for
human consumption. The total annual catch was
86,000 tons. In 1953, the first fish meal plants were
developed. Within 9 years, Peru became the number
one fishing nation in the world by volume. This lead
to a period of boom years in Peru. 1,700 purse
seiners exploited a 7-month fishing season.
Fearing a crash, in 1970, a group of scientists in the
Peruvian government issued a warning. They
estimated that the sustainable yield was around 9.5
million tons, a number that was currently being
surpassed (see Figure 4). The government turned a
deaf ear toward its own scientists. Due to the
Figure 4: Annual catch of the Peruvian
collapse of the Norwegian and Icelandic herring
Anchovy Fishery from 1960-1990
fisheries the previous year, Peru was more poised
than ever to earn yet more hard currency. Therefor, in 1970, the government allowed a
harvest of 12.4 million tons. The following year, 10.5 million tons were harvested. In 1972,
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the combination of an El Nino year and the prolonged overfishing led to a complete
collapse of the fishery. It has not recovered.
6. Maximum Sustained
Yield of the World's Oceans
To fish our waters more
sustainably, we need to
know what the sustained
maximum yield is. One
theoretical estimate puts
the estimated annual
production at 240 million
metric tons. The estimated
annual harvest is half of
this: 100-120 mmt. The
current annual harvest is
about 100 mmt.
Not all areas of the ocean
are equally productive
(Figure 5). As you can see
from this figure, the coastal
margins such as mangroves
and saltmarshes are much
more productive relative to
their volume than the open
ocean. Therefore, to
accurately estimate the
maximum yield of the
ocean, we must look at the Figure 5: Relative productivity of ocean zones
zones separately. The
estimate used above was obtained by dividing the ocean into three zones: open ocean,
coastal areas, and upwelling areas.
The estimate for the productivity of each of the three zones was estimated based on three
values: primary plant production, food chain length, and food chain efficiency. To further
understand the relationship these values and productivity, you may want to review some
lectures from last semester:
 The Flow of Energy: Primary Production explains how primary production is estimated
in marine waters, and
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 The Flow of Energy: Higher Trophic Levels discusses ecological efficiency of the food
chain and the loss of energy with each trophic transfer (the "10% Rule").
Figure 6 shows the areas of
highest phytoplankton
production. It is these areas
upon which we most rely for
our fish. Blooming across
large regions, phytoplankton
form large fields that sustain
the marine food web. A high
proportion of these
productive zones are found
where the ocean is rich in
minerals. 99% of the
worldwide annual
commercial ocean catch
comes from coastal waters,
within 200 nautical miles of
the coastline. These narrow
Figure 6: High phytoplankton production zones
coastal fringes of the world's
oceans are at once its most productive and most vulnerable zones. The following figure
(Figure 7) displays why these areas are most productive.
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Figure 7: Biological Productivity of the Oceans
Table 2: Estimated Production of Harvestable Fish
Open Ocean Coastal Waters
Upwelling Areas
Nutrient concentration low
intermediate
high
Primary Production
low
intermediate
high
Food Chain Length
long
intermediate
short
Ecological Efficiency
lower
------------>
higher
Fish Production
negligible
about half of total about half of total
A Paradox: "Fishing Down" reduces yields.
 Pauly, Dalsgaard and colleagues analyzed diet of 220 key species to assign each species of
catch to a trophic level (Science 279:860, 6 Feb 1998)
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 From 1950 to 1994, catch has gradually shifted from longlived, high-trophic level fish (e.g. cod and haddock) to lowtrophic-level fish and invertebrates such as anchovy and krill.
 Paradoxically, catches stagnated or declines, as competitors
(such as inedible jellyfish) fill the void. "If things go unchecked, we might end up with a
marine junkyard dominated by plankton."
7. Solutions
The increasing trend toward aquaculture may take some of the pressure off our overfished
seas. Between 1984 and 1994, aquaculture was the fastest growing supplier of fish
worldwide. Fish farms now account for more than 1/8th of the worlds catch. In China,
India, and Japan, aquaculture accounts for half of the total fish eaten. Aquaculture has
already eased some of the pressure on shrimp. Also, aquaculture allows for more optimal
use of feedgrains than the poultry or beef industury (this means less grain per pound is
needed for fish than those sources). However, there is some question about the long-term
sustainability of aquaculture. Negative impacts of aquaculture include disease, genetic
weakening of stocks, and coastal habitat destruction.
Downsize the existing fishing fleet. It is likely that a reduction of 30-50% will be required.
Reduce subsidies to the fishing industry. As seen in the following figure, currently the cost
of fishing outweighs the revenues 80 billion to 75 billion.
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International agreements of fish catch limits. International agreements
are crucial to prevent commercial extinction, as fish do not respect
international borders. This creates a "Tragedy of the Commons"
situation, where any fish that you do not take go into your neighbors
mouths. Although they rarely make the evening news, there have been
more fishery conflicts in the 1990's than in the whole 19th century. Some
examples are:
 The Cod Wars between Norway and Iceland
 Turbot Wars between Canada/Spain, Argentina/Taiwan, and China/Marshall Islands
 The Tuna Wars of the Northeast Atlantic
 Crab Wars of the Southwest Atlantic
 Squid Wars
 Pollock Wars in the Sea of Okhotsk
 The Salmon Wars of the Northern Pacific
What can you do?
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The above solutions need to be carried out by consensus among and within governments.
But you, by yourself, can make a difference by being an informed consumer. Don't buy
species of fish that are over-exploited, such as Atlantic Cod, Atlantic Sea Scallops, Black
Sea Bass, Farm Raised Shrimp, Gulf Shrimp, Monkfish, Redfish, Swordfish, Shark, Red
Snapper, Sturgeon, and Winter Flounder. Instead, order species like Alaska Salmon,
Pacific Coast Dungeness Crab, and trapped shrimp that are not currently overfished.
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